1. Field of the Invention
The present invention relates to novel photosensitive compounds and photosensitive resin compositions, as well as to a pattern formation method making use of such photosensitive compounds or resin compositions. The photosensitive compounds and photosensitive resin compositions exhibit not only high sensitivity and excellent storage stability, but also provide improved resolution. Thus, they have a wide range of utility, including, color cathode-ray tubes and other display tubes, screen printing, immobilized enzymes, PS (presensitized) plates and etching resists.
2. Description of the Related Art
Conventionally, negative-type photoresists used for the formation of black matrix and phosphor patterns of color cathode-ray tubes have made use of resists composed of a water-soluble polymer (such as polyvinyl alcohol) and a bichromate salt (hereinafter, resists of this type will be referred to as PVA-ADC-based resists). These negative-type photoresists have a fundamental disadvantage in that they require a special treatment facility for preventing environmental pollution, which is caused by the presence of bichromate salts.
To overcome the problem of environmental pollution, it has previously been considered to use compositions containing a water-soluble diazide compound (e.g., sodium 4,4'-diazidostilbene-2,2'-disulfonate (hereinafter abbreviated DAS) which serves as a photocrosslinking agent and a water-soluble polymer that is photocrosslinkable in the presence of the water-soluble diazide compound. Among such known photosensitive compositions are those containing, as photocrosslinkable water-soluble polymers, vinyl alcohol-maleic acid copolymers or salts thereof (Japanese Patent Application Laid-Open (kokai) No. 48-97602), vinyl alcohol-acrylamide copolymers (Japanese Patent Application Laid-Open (kokai) No. 48-97603), or water-soluble polyvinyl butyral (Japanese Patent Application Laid-Open (kokai) No. 48-98905). In practice, however, these compositions cannot be used because of their low sensitivity. Known compositions having sufficient sensitivity have been explored, including those containing polyvinylpyrrolidone (hereinafter abbreviated PVP) and a water-soluble bisazide compound serving as an additive (hereinafter, compositions of this type will be referred to as PVP-DAS-based resists; see, for example, Japanese Patent Application Laid-Open (kokai) No. 48-90185) and those containing an acrylamide-diacetoneacrylamide copolymer (hereinafter abbreviated PAD) and water-soluble bisazide serving as an additive (hereinafter, compositions of this type will be referred to as PAD-DAS-based resists; see, for example, Japanese Patent Application Laid-Open (kokai) No. 50-33764).
PVA-ADC-based resists, when used for the formation of black matrix of color cathode-ray tubes, present a drawback of poor resolution, in addition to the aforementioned problem of environmental pollution, due to low oxygen permeability and lack of reciprocity-law failure characteristics. In contrast, when PVP-DAS-based resists are used, due to their excessively high oxygen permeability, proper sensitivity cannot be obtained unless the thickness of coating film is increased, which in turn reduces resolution. On the other hand, PAD-DAS-based resists exhibit excellent sensitivity and resolution, but after they have undergone formation of resist patterns and coating of graphite, they provide poor etching characteristics, and, depending on the type of graphite, etching cannot be effected.
Regarding use for the formation of phosphor patterns, PVA-ADC-based resists are unsatisfactory in terms of both environmental pollution and sensitivity. In addition, chromium oxide, which remains after firing, degrades luminance of the phosphor. In this regard, both PVP-DAS-based resists and PAD-DAS-based resists have drawbacks in terms of sensitivity and therefore cannot be used.
Japanese Patent Application Laid-Open (kokai) Nos. 55-23163, 55-62905 and 56-11906 disclose non-chromium resists which are used for the formation of phosphor patterns and contain, as a photosensitive unit, a photosensitive resin resulting from a condensation reaction between polyvinyl alcohol and a quaternary ammonium salt (e.g., a styrylpyridinium salt or a styrylquinolinium salt) (hereinafter, resists of this type are referred to as PVA-SbQ-based resists).
Although these PVA-SbQ-based resists exhibit advantages such as shorter time required for photosensitization, they are not necessarily satisfactory in terms of resolution. Moreover, since their ionicity is limited to cationic, use and compositions of the resists are also limited. Furthermore, since a mercury lamp (365 nm) and a metal halide light source (400 nm) are used as light sources for exposure, 4-methylquinoline or a similar substance must be used to set the photosensitive wavelength of the resists in a longer wavelength range. This is adds the drawback of increased costs.
Methods for the formation of color filters for use with color cathode-ray tubes are disclosed in, Japanese Patent Application Laid-Open (kokai) Nos. 5-266795, 8-87962, 8-185799 and others. All of these methods employ dichromate salts as crosslinking agents, and therefore are not completely satisfactory in view of disadvantages such as environmental pollution, low sensitivity and intricate processing.
As described above, there are no conventional photoresists that simultaneously satisfy the requirements of environmental pollution, sensitivity and resolution. Therefore, in certain uses, such as color cathode-ray tubes, other display tubes and screen printing, there is still a need for resists that exhibit excellent sensitivity at a wavelength as long as 400 nm and that are dissolvable or dispersible in an aqueous solvent. Particularly, in consideration of the excellent characteristics of polyvinyl alcohol (hereinafter abbreviated PVA) in use for the formation of phosphor patterns, a demand exists for PVA-based resists of a certain type which have a longer photosensitive wavelength than the wavelength possessed by PVA-SbQ-based resists, and in addition, permit selection between anionic and nonionic depending on their use.
Also, there exists a need for a pattern formation method making use of a composition which exhibits high sensitivity, improved adhesion to a substrate, excellent coating characteristics and stability during storage. There exists a Particularly, there is a need for a pattern formation method in which an advantage related to reciprocity-law failure characteristics, which can be obtained when a water-soluble polymer and a water-soluble azide compound is used in combination, is maintained, and that makes use of a photosensitive composition which exhibits high sensitivity, has improved adhesion characteristics to a substrate, exhibits excellent coating characteristics and stability during storage.